From 04da295f49e587a06f28f6e55f22ca17d5b69731 Mon Sep 17 00:00:00 2001
From: Agetian <Agetian@269b9781-a132-4a9b-9d4e-f004f1b56b58>
Date: Sun, 24 Sep 2017 04:48:07 +0000
Subject: [PATCH] - Some improvements to DoNotDiscardIfAble discard AI for
 corner cases, to avoid (very rare) situations where the AI would not discard
 anything or crash.

git-svn-id: http://svn.slightlymagic.net/forge/trunk@35736 269b9781-a132-4a9b-9d4e-f004f1b56b58
---
 .../src/main/java/forge/ai/AiController.java  | 23 +++++++++++++++++++
 .../main/java/forge/ai/ComputerUtilCard.java  |  4 ++++
 2 files changed, 27 insertions(+)

diff --git a/forge-ai/src/main/java/forge/ai/AiController.java b/forge-ai/src/main/java/forge/ai/AiController.java
index 64218470..79cf3567 100644
--- a/forge-ai/src/main/java/forge/ai/AiController.java
+++ b/forge-ai/src/main/java/forge/ai/AiController.java
@@ -943,6 +943,29 @@ public class AiController {
                         // for more discard options
                         worst = ComputerUtilCard.getCheapestSpellAI(validCards);
                     }
+                    if (worst == null && !validCards.isEmpty()) {
+                        // still nothing chosen, so choose the first thing that works, trying not to make DoNotDiscardIfAble
+                        // discards
+                        for (Card c : validCards) {
+                            if (!c.hasSVar("DoNotDiscardIfAble")) {
+                                worst = c;
+                                break;
+                            }
+                        }
+                        // Only DoNotDiscardIfAble cards? If we have a duplicate for something, discard it
+                        if (worst == null) {
+                            for (Card c : validCards) {
+                                if (CardLists.filter(player.getCardsIn(ZoneType.Hand), CardPredicates.nameEquals(c.getName())).size() > 1) {
+                                    worst = c;
+                                    break;
+                                }
+                            }
+                            if (worst == null) {
+                                // Otherwise just grab a random card and discard it
+                                worst = Aggregates.random(validCards);
+                            }
+                        }
+                    }
                     discardList.add(worst);
                     validCards.remove(worst);
                 }
diff --git a/forge-ai/src/main/java/forge/ai/ComputerUtilCard.java b/forge-ai/src/main/java/forge/ai/ComputerUtilCard.java
index 41358158..b4a5e183 100644
--- a/forge-ai/src/main/java/forge/ai/ComputerUtilCard.java
+++ b/forge-ai/src/main/java/forge/ai/ComputerUtilCard.java
@@ -374,6 +374,10 @@ public class ComputerUtilCard {
                     Predicates.or(CardPredicates.isType("Instant"), CardPredicates.isType("Sorcery")));
             Collections.sort(cc, CardLists.CmcComparatorInv);
 
+            if (cc.isEmpty()) {
+                return null;
+            }
+
             Card cheapest = cc.getLast();
             if (cheapest.hasSVar("DoNotDiscardIfAble")) {
                 for (int i = cc.size() - 1; i >= 0; i--) {